Topic
Tagged Command Queuing
About: Tagged Command Queuing is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 51 citations. The topic is also known as: TCQ.
Papers
Patent•
IBM1
TL;DR: In this article, the SAF-TE Processor (SEP) is used to check in with its current status before a status change occurs, and the host adapter is prepared for receiving asynchronously a changed status from the reconnecting target device whenever it becomes available, without resorting to use of a complex SCSI protocol known as asynchronous event notification.
Abstract: A method for determining a change in the SAF-TE enclosure status and a change in the SAF-TE device slot status, each with a single issuance of one new command, replacing countless re-issuance of similar commands. Use is made of a common disconnection/reconnection capability as well as a tagged command queuing technique, such that multiple types of status changes in a SAF-TE enclosure are concurrently determined. Since each of the new commands described here is initiated by the host adapter, the host adapter is prepared for receiving asynchronously a changed status from the reconnecting target device such as a SEP whenever it becomes available, without resorting to use of a complex SCSI protocol known as “asynchronous event notification.” Status fields in the data packets transferred by the commands introduced in this invention may be the same as those in conventional systems, and so the inventive commands are a natural extension to conventional systems and may be adapted while maintaining compatibility with existing hardware and protocols. Removes stringent SEP response time requirements and causes negligible host system performance impact independent of how many SAF-TE enclosures are attached to the host adapter. Provides for use of an optional convenience timer for the SAF-TE Processor (SEP) device to check in with its current status before a status change occurs. Maintains backward compatibility by detection of an absence of the “tagged command queuing” indicator in inquiry data from the SEP device with implementations that do not support the inventive commands. Computer software and firmware implementations are provided.
35 citations
Patent•
29 Jul 1996
TL;DR: In this article, the issue number with the upper-limit value of the number of issued tagged command queuing (TCQ) commands in device ID units is used to detect the issue of TCQ commands exceeding the upper limit value and enqueue them.
Abstract: PROBLEM TO BE SOLVED: To sufficiently derive the performance of a magnetic disk drive and to speed up processing without making a request exceeding the performance by setting the upper-limit value of the number of issued tagged command queuing(TCQ) commands in device ID units SOLUTION: An information processor 1 which is connected to magnetic disk drives 5 and 6 through a SCSI bus 7 makes the TCQ command issue of the SCSI control driver 3 of an OS 2 efficient and consists of a command issue processing part 33, a command end processing part 34, and a current counter 31 and a save counter 32 provided in a memory 4 The current counter 31 stores the number of commands which are issued by the SCSI control driver 3 and being executed in ID units and the save counter 32 stores a permissible upper-limit value in ID units The command issue processing part 33 compares the issue number with the upper-limit value to previously detect the issue of TCQ commands exceeding the upper-limit value and enqueue them The command end processing part 34 subtracts the issue number in end response and sets the current issue num ber to the upper-limit value of the save counter 32 in queue-full response
8 citations
Patent•
11 Apr 2000
TL;DR: In this paper, a method and system are disclosed for processing tagged commands from a Fibre Channel host (14, 22) in a fibre channel network (10) to one or more SCSI streaming target devices (18, 28, 32, 34) through an SCSI route (16, 30).
Abstract: A method and system are disclosed for processing tagged commands from a Fibre Channel host (14, 22) in a Fibre Channel network (10) to one or more SCSI streaming target devices (18, 28, 32, 34) through an SCSI route (16, 30). The method includes the step of determining whether the command is a tagged command. If the command is a tagged command, then the command processing method of the current invention determines whether the intended target device (18, 28, 32, 34) is a streaming target device. If the intended target device (18, 28, 32, 34) is a streaming target device, the method and system of the present invention can convert the command's format from a tagged command format to an un-tagged format and forward the command to the intended target device (18, 28, 32, 34). Flags in an internal SCSI router register (17, 19) can be set to track which, if any, devices attached to the SCSI router (16, 30) can support tagged commands. Upon completion of the command, the method of the present invention can forward the command complete message to the issuing Fibre Channel host (14, 22).
8 citations
Performance Metrics
| Year | Papers |
|---|---|
| 2000 | 2 |
| 1996 | 1 |